Is an hibryd amp solid/tube a good choice ?

I can't speak for the amps you mention above, but I use a rebuilt Counterpoint hybrid amp and I love the combiantion of tube and SS characteristics. I would assume that the AR is better than the NAK, but I could be wrong.

I had a Music Reference RM-200 that was fantastic. It was so good that after I sold the first one and replaced it with a BAT VK60, I sold the BAT and bought another RM-200. Very transparent, tight bass and wonderful detail even at low levels. They pop up every once and a while on this site, but seem to sell quickly. The amp received great reviews from Mike Fremmer, he loved it, could not say enough about it. A great sounding amp for a reasonable price!
Good luck and let your ears be the judge.